WASHINGTON — President Trump said on Thursday that he planned to issue a pardon to Dinesh D’Souza, a conservative author, commentator and filmmaker, and was strongly considering commuting the sentence of former Gov. Rod Blagojevich of Illinois, a Democrat.
Flexing his clemency power as he and his team face multiple criminal investigations of their own, Mr. Trump also said that he was looking at the case of Martha Stewart, the lifestyle mogul who spent five months in prison for lying to investigators about the timing of a stock sale.
The pardon for Mr. D’Souza, who pleaded guilty in 2014 to making illegal campaign contributions, represents a victory for one of the president’s most vocal bases of support, the conservative media. Mr. D’Souza has argued that he was singled out for prosecution because of his conservative politics.
“He was treated very unfairly by our government!” Mr. Trump said of Mr. D’Souza in a Twitter post.
The pardon will be the fifth that Mr. Trump has issued. Last year, the president pardoned Joe Arpaio, the former Arizona sheriff, a move that was also popular among Mr. Trump’s conservative base, especially the anti-immigrant contingent.
The D’Souza pardon comes as one of Mr. Trump’s personal lawyers, Michael D. Cohen, is under investigation for possibly violating federal campaign finance laws. Mr. Trump’s lawyers and aides have become resigned to the possibility that Mr. Cohen could offer information to the authorities about work he did for Mr. Trump, and critics of the president said the latest pardon could be a signal to Mr. Cohen that he would be pardoned, too, if he declined to cooperate with federal officials.
Both Mr. D’Souza and Mr. Trump are prolific Twitter posters, though Mr. D’Souza has a small fraction of the president’s followers. Mr. D’Souza has promoted conspiracy theories and regularly posts about what he calls “fake news.” He also supports Mr. Trump’s unproven claim that the F.B.I. planted a spy inside the Trump campaign.
Mr. D’Souza turned to Twitter on Thursday to thank the president and his supporters for the pardon. He repeated his contention that the prosecution was politically driven, criticizing Mr. Obama and his administration.
Mr. D’Souza’s wife, Debbie D’Souza, thanked Senator Ted Cruz, Republican of Texas, for pushing Mr. Trump for the pardon.
Mr. Cruz also tweeted his praise and said Mr. D’Souza was “the subject of a political prosecution.”
Mr. D’Souza, who once accused former President Barack Obama of executing the “anticolonial” agenda of his Kenyan father, entered a guilty plea in 2014 to avoid up to two years of prison time. A judge in Federal District Court in Manhattan sentenced Mr. D’Souza to five years of probation, including eight months in a supervised “community confinement center.”
He was accused of using straw donors to contribute to a 2012 Republican Senate candidate in New York, Wendy E. Long. Ms. Long was a classmate from Dartmouth College, where they worked together on the staff of The Dartmouth Review, a conservative campus newspaper.
She was running against Senator Kirsten E. Gillibrand, a Democrat. Prosecutors said that Mr. D’Souza lied to Ms. Long about the donations.
Mr. Trump has praised Mr. D’Souza’s political commentary, and in 2012 he encouraged people to see Mr. D’Souza’s documentary “2016: Obama’s America,” calling it an “Amazing film!” Mr. D’Souza said recently on his website that he has a new movie coming out this summer.
Mr. D’Souza was not eligible to apply for a pardon through the Justice Department, which requires a five-year waiting period from the date of conviction to apply. But the president has the power to pardon any person convicted of a federal crime.
“Donald Trump has sent a message to his friends and cronies that if you break laws to protect him or attack our democracy, he’s got your back,” said David Donnelly, president of the watchdog group Every Voice. “Contribution limits are a key bulwark against corruption in politics, and pardoning the man who knowingly violated them is in direct conflict with his pledge to drain the swamp in Washington.”
Mr. Trump has also issued pardons for the boxing legend Jack Johnson; I. Lewis Libby Jr., a former aide to Dick Cheney; and Kristian Saucier, a former Navy sailor.